IA on effect of temperature on polyphenol (tannins) quantification using potassium permanganate titration (Lowenthal permanganate).
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The document discusses the quantification of polyphenols (tannins) using potassium permanganate titration, emphasizing the effect of temperature on this process. It outlines the preparation of potassium permanganate and indigo carmine, along with the procedure for titration, which involves immersing pure grape extract in varying temperatures. The study highlights limitations, assumptions, and provides a formula for calculating total polyphenol concentration based on titration results.
IA on effect of temperature on polyphenol (tannins) quantification using potassium permanganate titration (Lowenthal permanganate).
- 1. Effect of temp on polyphenol (tannins) quantification using potassium permanganate titration (Lowenthal permanganate) Polyphenols are antioxidants : - found in blackberry, wines, blueberry, cranberry, grapes, cider, citrus fruits - Tannins (TA), flavonoids, catechins, EGCG, EGC, ECG. - quantification using potassium permanganate (titration) - using indigo carmine indicator (blue) to green yellow Antioxidants that can be quantified using permanganate titration Procedure: Potassium permanganate 0.004M (0.02N) was prepared. 0.1% (w/v) indigo carmine indicator 0.1g in 100ml acidified with H2SO4. End point is greenish yellow. Limitation : antioxidants like Vit C will be included Assumption - all antioxidants esp polyphenol will be quantified. Effect of temp (15, 45, 55, 65, 75) will be studied, using water bath. Click here, here, here , here for research papers
- 2. Green/red grapes – pure extract using cheese cloth Indicator change from blue to greenish yellow Procedure: Potassium permanganate 0.004M (0.02N) was prepared. 0.1% indigo carmine indicator 0.1g in 100ml acidified with H2SO4. End point is greenish yellow. 0.5ml of pure extract (grapes juice) added to centrifuge tube. Extract was immersed into water bath at various temp for 10 mins. After 10 mins, 2ml water and 200ul of indigo carmine were added. Blue sol obtained. Titrated with 0.004M KMnO4 until end point is seen. Ini and final vol recorded. Blank titration was done – 2 ml water and 200ul indicator without any antioxidants Temp/C Ini vol Final vol Vol (X) KMnO4 Polyphenol mg/L TA 15 3.9 4.7 0.8 498 45 11.5 12.2 0.7 415 55 12.3 12.8 0.5 249 65 18.0 18.6 0.6 332 75 20.9 21.4 0.5 249 Blank (Y) 4.7 4.9 0.2 -- End point Effect of temp on polyphenol (tannins) quantification using potassium permanganate titration (Lowenthal permanganate) Green grapes Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000 (0.8 - 0.2) x 4.157 x 0.02 x 10000 = 498mg/L Formula that can be used. Click here for reference Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000 4.157 – conversion factor to TA equivalents 10000 – conversion factor from % to mg/L of TA. N – normality for KMnO4 which is 0.02N or 0.004M X – Vol KMnO4 used Y – Vol blank titration TA – tannic acid
- 3. Green/red grapes – pure extract using cheese cloth Effect of temp on polyphenol (tannins) quantification using potassium permanganate titration (Lowenthal permanganate) End point Temp/C Ini vol Final vol Vol (X) KMnO4 Polyphenol mg/L TA 15 3.9 4.7 0.8 498 45 11.5 12.2 0.7 415 55 12.3 12.8 0.5 249 65 18.0 18.6 0.6 332 75 20.9 21.4 0.5 249 Blank (Y) 4.7 4.9 0.2 -- Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000 (0.8 - 0.2) x 4.157 x 0.02 x 10000 = 498mg/L Formula that can be used. Click here for reference Total polyphenol (mg/L TA) = (X – Y) x 4.157 x conc KMnO4 (N) x 10000 4.157 – conversion factor to TA equivalents 10000 – conversion factor from % to mg/L of TA. N – normality for KMnO4 which is 0.02N or 0.004M X – Vol KMnO4 used Y – Vol blank titration TA – tannic acid 0 0.2 0.4 0.6 0.8 1 15 45 55 65 75 Blank (Y) vol KMnO4 temp Temp/C vs Vol KMnO4 0 200 400 600 15 45 55 65 75 Total polyphenol/mg/L TA temp/C Temp/C vs Total polyphenol/mg/L TA 0 200 400 600 0 20 40 60 80 Total polyphenol/mg/L TA Temp/C Temp/C vs Total polyphenol/mg/L TA
- 4. Oxidizing Agent Reducing Agent MnO4 - Fe2+ Cr2O7 2- SO2 HNO3 I- H2O2 H2S CI2 SO3 2- KIO3 Vitamin C OCI-/Cu2+ Oxalate/ C2O4 2- Titration Redox Titration Acid Base Titration Burette/Titrant Oxidizing agent ? Acid/Base Titration Redox Titration Neutralization bet acid/base Redox bet oxidizing/reducing agent Transfer proton/H+ from acid to base Transfer elec from reducing to oxidizing agent Indicator for colour change No indicator needed Redox Titration - One reactant – must be standard (known conc) or capable being standardised - Reaction bet Oxidizing agent/Titrant with Reducing agent/Analyte - Titrant of known concentration - Stoichiometrically equivalent amt titrant/titrand added - No indicator needed. Detectable by colour change of Oxidizing/Reducing agent Analyte/reducing agent Titrand Redox Titration used to determine: - Amount of copper in brass - Amount Fe/iron in iron pill/food - Amount H2O2 commercial peroxide solution - Amount OCI - /hypochlorite/CI2 in bleach - Amount Vitamin C - Amount Dissolve oxygen content/BOD - Amount ethanol in beer/wine - Amount oxalate acid ? MnO4 - + 5Fe2+ + 8H+ → Mn2+ + 5Fe3+ + 4H2O Cr2O7 2- + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ 7H2O Iron determination using MnO4 - / Cr2O7 2- purple colourless orange green add MnO4 - till endpoint ↓ turn purple (excess MnO4 - ) add Cr2O7 2- till endpoint ↓ turn orange (excess Cr2O7 2-)